Semiconductor integrated circuit device including a memory device having memory cells with increased information storage capacitance and method of manufacturing same

ABSTRACT

A semiconductor memory device has a semiconductor substrate, and memory cells provided at intersections between word line conductors and bit line conductors. Adjacent two memory cells for each bit line conductor form a memory cell pair unit structure, in which first semiconductor regions of the transistors of the adjacent two memory cells are united at their boundary into a single region and are connected to one of the bit line conductors via a bit line connection conductor, the gate electrodes of the transistors of the adjacent two memory cells are connected to word line conductors adjacent to each other, respectively, and the second semiconductor regions of the transistors of the adjacent two memory cells are connected to the respective information storage capacitors. A series of memory cell pair unit structures formed under one bit line conductor is positionally shifted with respect to series of memory cell pair unit structures formed under adjacent first and second bit line conductors on opposite sides of the one bit line conductor, respectively, such that a second information storage capacitor of a memory cell pair unit structure formed under the adjacent first bit line conductor and a first information storage capacitor of a memory cell pair unit structure formed under the adjacent second bit line conductor are located adjacent to a bit line connection conductor of a memory cell pair unit structure formed under the one bit line conductor.

This application is a continuation application of application Ser. No.08/731,489, filed Oct. 16, 1996, now U.S. Pat. No. 5,831,300, which is acontinuation application of application Ser. No. 08/341,966, filed Nov.16, 1994, now U.S. Pat. No. 5,578,849.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor integrated circuitdevice and manufacturing techniques therefor, and more particularly totechniques which are effectively applied to a semiconductor integratedcircuit device having a DRAM (Dynamic RAM). It is first noted that inthe following description, an n-channel MOS FET is abbreviated as "nMOS"and a p-channel MOS FET as "pMOS".

The number of bits in DRAMs has been increased greatly. This is becausethe DRAM has characteristics suitable for enhancing the integrationdegree: for example, the cell structure of a DRAM is rather simple amongall kinds of semiconductor memories; the pattern design is regularlymade so that a large scaled design is possible for the DRAM; the cellarea can be made small; and so on.

With further progressive increases in the number of bits in DRAMs, animportant problem to be solved is how to ensure a sufficient storagecapacitance or capacitors constituting memory cells in the DRAM. Thisproblem is caused mainly by the use of a lower voltage in the DRAM,which lower voltage is promoted in view of reduction in an area occupiedby each memory cell and in order to ensure the reliability of thedevice.

FIG. 74 shows an example of a partial plan view of a conventional memorycell array. A memory cell array 50 includes word line conductors(identified by shaded areas) 51 extending in the vertical direction,when viewed on FIG. 74, which are repetitively arranged along thehorizontal direction on FIG. 74.

Bit line conductors 52 extending orthogonal or perpendicular to the wordline conductors 51 are repetitively arranged in the vertical directionas viewed in FIG. 74. On both sides of each bit line connector 54connecting a bit line conductor 52 and a MOS FET (hereinafter simplyabbreviated as "MOS") 53, memory cells 55 are arranged. Each of thememory cells 55 is constituted of the MOS 53 and a capacitor 56. Thecapacitor 56 includes a node electrode 58 provided separately for eachindividual memory dell, a plate electrode 59 provided in common toplural memory cells and a dielectric film sandwiched therebetween.

Conventionally, the memory cells 55 are positionally shifted by one-halfof a periodic pattern alternately to the left and to the right on FIG.74 each time the bit line conductor 52 is repetitively arranged. Forthis reason, the capacitors 56 in the plurality of memory cells 55 arelinearly aligned in the vertical direction on FIG. 74.

The following references disclose respective proposals of layouts ofmemory cells:

a. JP-A-5-13673 (laid open on Jan. 22, 1993);

b. JP-A-3-72675 (laid open on Mar. 27, 1991); and

c. JP-A-6-5811 (laid open on Jan. 14, 1994).

Formation of channel stoppers by ion implantation through fieldinsulating films formed by the LOCOS technique is shown, for example, inthe following references:

d. Extended Abstract of the 21st Conference on Solid State Devices andMaterials, Tokyo, 1989, pp. 105-108;

e. JP-A-56-87340 (laid open on Jul. 15, 1981);

f. JP-A-62-298161 (laid open on Dec. 25, 1987) corresponding to U.S.Pat. No. 5,116,775; and

g. U.S. Pat. No. 3,860,454 (issued on Jan. 14, 1975).

Examples of structures for electrical connection between bit lineconductors and switching transistors of memory cells are disclosed inthe following references:

h. Sakaw, et al., "A Capacitor-Over-Bit-Line (COB) Cell With aHemispherical-Grain Storage Node for 64 Mb DRAMs", in IEDM '90, pp.655-658; and

i. JP-A-5-259405 (laid open on Oct. 8, 1993).

Further, examples of structures of an information storage capacitor of amemory cell are disclosed in the following references:

i. JP-A-5-226583 (laid open on Sep. 3, 1993);

k. JP-A-6-77428 (laid open on Mar. 18, 1994); and

l. JP-A-5-82750 (laid open on Apr. 1, 1993).

SUMMARY OF THE INVENTION

However, the present inventors, as a result of investigatingconventional techniques, found that the conventional memory cellstructure has the following problems.

First, as shown in FIG. 74, since the conventional memory cell structurehas the capacitors 56 (particularly node electrodes 58 of thecapacitors) in the memory cells 55 linearly aligned along the verticaldirection on FIG. 74, an area to be allotted to each capacitor can nolonger be increased, considering that a spacing should be ensured forseparating adjacent capacitors 56 from each other. This linearly alignedconfiguration gives rise to structural defects. Also, this structuremakes it difficult to take a positioning margin between the adjacentcapacitors 56 and capacitor connectors 57 (a portion for achieving anelectric connection with a source or a drain of a MOS).

It is therefore an object of the present invention to provide techniqueswhich enable the area of a capacitor constituting a memory cell to beincreased without incurring an excessive increase in the entire area ofa memory cell array. This results in improving an α-ray resistivity ofthe memory cell, and increasing an output signal from the memory cell.

According to one aspect of the present invention, there is provided asemiconductor memory device comprising a semiconductor substrate, aplurality of word line conductors and a plurality of bit line conductorsformed over the substrate, and a plurality of memory cells each providedat an intersection between one of the word line conductors and one ofthe bit line conductors, wherein:

adjacent two memory cells for each bit line conductor form a memory cellpair unit structure, in which each of the memory cell pair unitstructures includes a first information storage capacitor, a firstswitching transistor, a second switching transistor and a secondinformation storage capacitor arranged in the described order under oneof the bit line conductors in a lengthwise direction of the bit lineconductors, each of the transistors having a pair of semiconductorregions formed in the substrate and a control electrode formed betweenthe pair of semiconductor regions over the substrate, an electriccurrent being caused to flow between the pair of semiconductor regionswhen the transistor is conductive responsive to a control signal appliedto the control electrode, one of the pair of semiconductor regions ofthe first transistor and one of the pair of semiconductor regions of thesecond transistor being united at their boundary into a single regionand being connected to one of the bit line conductors via a bit lineconnection conductor, the gate electrodes of the first and secondtransistors being connected to word line conductors adjacent to eachother, respectively, the others of the pair of semiconductor regions ofthe first and second transistors being connected to the first and secondinformation storage capacitors, respectively, the first informationstorage capacitor and the first switching transistor forming one of theadjacent two memory cells, the second information storage capacitor andthe second switching transistor forming the other of the adjacent twomemory cells; and

a series of memory cell pair unit structures formed under one bit lineconductor is positionally shifted with respect to a series of memorycell pair unit structures formed under adjacent first and second bitline conductors on opposite sides of the one bit line conductor,respectively, in a direction parallel with the bit lines such that asecond information storage capacitor of a memory cell pair unitstructure formed under the adjacent first bit line conductor and a firstinformation storage capacitor of a memory cell pair unit structureformed under the adjacent second bit line conductor are located adjacentto a bit line connection conductor of a memory cell pair unit structureformed under the one bit line conductor, as viewed in a directionperpendicular to the substrate.

According to another aspect of the present invention, in a semiconductorintegrated circuit device having a semiconductor substrate, word lineconductors formed over the substrate, bit line conductors orthogonal orperpendicular thereto, and DRAM cells including switching transistorsand information storage capacitors arranged at intersections of the wordline conductors and the bit line conductors on the substrate, bit lineconnection members each for connecting one bit line conductor to thetransistors of its associated DRAM cells are positionally shifted in apredetermined direction by a distance, each time the bit line conductoris repeatedly arranged, so that a bit line connection member for one bitline conductor and a bit line connection member for an adjacent bit linenearest to the first-mentioned bit line are on opposite sides of a wordline conductor.

According to another aspect of the present invention, a method ofmanufacturing the semiconductor integrated circuit device comprises thestep of properly implanting predetermined impurity ions into apredetermined region in the semiconductor device, after a fieldinsulating film is formed on the semiconductor substrate, for forming achannel stopper layer for element separation in a DRAM cell array and aperipheral circuit region.

According to another aspect of the present invention, a method ofmanufacturing a semiconductor integrated circuit device comprises thesteps of:

(a) depositing a low-resistance polysilicon film, after forming firstcontact holes each for exposing one semiconductor region of thetransistor through a first insulating film covering the DRAM cells andthe transistors, in such a degree that the top surface thereof is madesubstantially planar;

(b) etching back an upper portion of the low-resistance polysilicon filmso as to leave the low-resistance polysilicon film only in the firstcontact holes;

(c) diffusing predetermined impurities from the low-resistancepolysilicon film filled in the first contact holes to the onesemiconductor region;

(d) forming second contact holes reaching elements in the peripheralcircuit region through the first insulating film, and thereafterdepositing a pre-determined metal film over the semiconductor substrate;and

(e) patterning the metal film to form bit line conductors electricallyconnected to the low-resistance polysilicon film filled in the firstcontact holes to constitute memory circuits and first level wiringconductors electrically connected to the elements to constituteperipheral circuits.

According to another aspect of the present invention, a method ofmanufacturing a semiconductor integrated circuit device which includesDRAM cells each having a capacitor of a stacked fin structure has, priorto depositing conductive films for forming second and subsequent fins, astep of flattening an insulating film underlying the conductive filmafter forming first fins of the capacitors of the stacked fin structure.

According to another aspect of the present invention, a method ofmanufacturing a semiconductor integrated circuit device which includesDRAM cells each having a capacitor formed of a plurality of stacked finscomprises the steps of:

(a) depositing a first conductive film for forming a first fin for eachof the fin-shaped capacitors, after forming contact holes each forexposing one semiconductor region of the transistor through aninsulating film for covering the transistor;

(b) etching back an upper portion of the first conductive film toflatten the top surface thereof; and

(c) forming second and subsequent fins for each of the capacitors on theflattened top surface of the first conductive film.

According to anther aspect of the present invention, a method ofmanufacturing a semiconductor integrated circuit device which includesDRAM cells each having a capacitor of a stacked fin structure comprisesthe steps of:

(a) depositing, after forming a protective insulating film on a firstinsulating film covering the transistors, a second insulating film onthe protective insulating film, an etching rate of the second insulatingfilm being different from that of the protective insulating film;

(b) forming a first conductive film for forming a first fin for each ofthe capacitors of the stacked fin structure in such a degree that thetop surface thereof is flattened, after forming contact holes each forexposing one semiconductor region of the transistors through the firstinsulating film, the second insulating film and the protectiveinsulating film;

(c) etching back the top surface of the first conductive film to flattenthe top surface thereof;

(d) depositing a second conductive film for forming second andsubsequent fins for each of the capacitors on the flattened top surfaceof the first conductive film with a third insulating film beinginterposed therebetween; and

(e) removing the third insulating film interposed between the secondinsulating film and the fins with the protective insulating film beingused as an etching stopper layer, after the first conductive film andthe second conductive film are patterned.

The above and other objects and novel features of the present inventionwill become apparent from the description of the preferred embodimentswhen read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a main portion of a semiconductorintegrated circuit device according to one embodiment of the presentinvention;

FIG. 2A and FIG. 2B are cross-sectional views taken along line IIA--IIAand line IIB--IIB in FIG. 1, respectively;

FIG. 3 is a partial sectional view showing a peripheral circuit regionof the semiconductor integrated circuit device illustrated in FIG. 1;

FIG. 4 is a plan view showing another main portion of the semiconductorintegrated circuit device illustrated in FIG. 1;

FIGS. 5-46 are cross-sectional views each showing a main portion of asemiconductor substrate including a memory cell array andcross-sectional views each showing a main portion of the semiconductorsubstrate including a peripheral circuit at a variety of stages ofmanufacturing the semiconductor integrated circuit device illustrated inFIG. 1;

FIGS. 47-56 are cross-sectional views each showing a main portion of asemiconductor substrate including a memory cell array at a variety ofstages of manufacturing a semiconductor integrated circuit deviceaccording to another embodiment of the present invention;

FIGS. 57-65 are cross-sectional views each showing a main portion of asemiconductor substrate including a memory cell array at a variety ofstages of manufacturing a semiconductor integrated circuit deviceaccording to a further embodiment of the present invention;

FIGS. 66-71 are cross-sectional views each showing a main portion of asemiconductor substrate including a memory cell array andcross-sectional views each showing a main portion of the semiconductorsubstrate including a peripheral circuit at a variety of stages ofmanufacturing a semiconductor integrated circuit device according to afurther embodiment of the present invention;

FIG. 72 is a cross-sectional view showing a main portion of asemiconductor integrated circuit device including a memory cell arrayaccording to a further embodiment of the present invention;

FIG. 73 is a cross-sectional view showing a main portion of asemiconductor integrated circuit device including a memory cell arrayaccording to a further embodiment of the present invention;

FIG. 74 is a plan view showing part of a memory cell array-ofa-conventional DRAM; and

FIG. 75 shows a connection circuit diagram of memory cell array portionsin the semiconductor integrated circuit devices shown in FIGS. 1 and 74.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(Embodiment 1)

FIG. 1 is a plan view showing a main portion of a semiconductorintegrated circuit device according to one embodiment of the presentinvention; FIG. 2A is a cross-sectional view taken along line IIA--IIAin FIG. 1; FIG. 3 is a partial cross-sectional view showing a peripheralcircuit region of the semiconductor integrated circuit device; and FIGS.5-46 are cross-sectional views each showing a main portion of asemiconductor substrate and associated layers at a variety of stages ofmanufacturing the semiconductor integrated circuit device illustrated inFIG. 1.

The semiconductor integrated circuit device of Embodiment 1 may be, forexample, a 64-megabit DRAM device. A main portion of a memory cell arraythereof is shown in FIG. 1.

In a memory cell array M, a plurality of word line conductors WLextending in the vertical direction in FIG. 1, which are made of, forexample, n-type low-resistance polysilicon, are repetitively arrangedover a semiconductor substrate 1 at predetermined intervals along thehorizontal direction in FIG. 1. For facilitating recognition, word lineconductors WL in FIG. 1 are filled with hatching.

A plurality of bit line conductors BL extending orthogonally to theextending direction of the word line conductors WL are made of metalsuch as tungsten, by way of example, and repetitively arranged atpredetermined intervals along the vertical direction in FIG. 1 over thesemiconductor substrate 1.

When viewed from the direction perpendicular to the semiconductorsubstrate 1 with respect to each bit line conductor BL, memory cells MCare arranged on both sides of a bit line connection member BC forelectrically connecting nMOS regions on the semiconductor substrate 1.Each of the memory cells MC is constituted of, for example, a switchingtransistor (nMOS 2 in this example) and a capacitor 3. Reference CCrepresents a capacitor connection portion which specifically includes acontact hole (FIG. 2A) for electrically connecting one of twosemiconductor regions for a source and a drain of the nMOS 2 with thecapacitor 3 and a contact hole 12f (FIG. 27) between a first fin 3a1 anda second fin 3a2 in the capacitor 3.

Each nMOS 2 is arranged between the bit line connection member BC andthe capacitor connection portion CC, and a portion of the word lineconductor WL lying therebetween also serves as a gate electrode 2g ofthe nMOS 2. Thus, adjacent two memory cells constitute a memory cellpair unit structure. The nMOS 2 and the capacitor 3 will be describedlater.

It should be noted in Embodiment 1 that as the bit line connectionmembers BC are positioned in the downward direction in FIG. 1, i.e., inthe direction in which the word line conductors WL extend, the bit lineconnection member for one bit line conductor and a bit line connectionmember for an adjacent bit line conductor nearest to the first-mentionedbit line connection member are on opposite sides of a word lineconductor, i.e., the latter bit line connection member is shifted withrespect to the former one in the direction in which the bit lineconductors BL extend. Stated another way, as the bit line conductors BLare repetitively arranged in the downward direction in FIG. 1, thememory cells MC are shifted by a distance substantially corresponding toan arrangement pitch of the word line conductors WL in the rightdirection in FIG. 1.

It may be thought that the memory cell pair unit structure isgeometrically constituted of a bit line connection member BC, two memorycells MC on both sides thereof, and a separating space betweencapacitors of these two memory cells and capacitors 3 of memory cellsadjacent to these two memory cells. Then, each time the bit lineconductor BL is repetitively arranged in the downward direction in FIG.1, a series of the unit structures is shifted by a quarter of the lengthof a periodic pattern in the right direction in FIG. 1. Therefore, thearrangement of the memory cells MC described above is repeated for everyfour bit line conductors BL.

Also, in Embodiment 1, the capacitors 3 are arranged near four sides ofeach bit line connection member BC, as illustrated in FIG. 1. Statedanother way, the bit line connection member BC in a unit structureformed under a bit line conductor is also adjacent to the capacitors 3of one and the other unit structures formed under two bit lineconductors adjacent to the bit line conductor, so that the bit lineconnection member BC is consequently surrounded by such four capacitors3. Then, the distances from the bit line connection member BC to thefour capacitors 3 near the four sides thereof are substantially equal.In other words, uniform repetition is ensured.

In Embodiment 1, by virtue of the arrangement of the memory cells MC asdescribed above, the following effects, for example, can be produced.

First, since the capacitors 3 are not sequentially placed under adjacentbit line conductors along the vertical direction in FIG. 1, the distancebetween the adjacent capacitors 3 can be elongated in the verticaldirection in FIG. 1, and the distance may be used as an extended regionfor each of the capacitors 3.

Second, since the capacitors 3 will not be sequentially placed in thevertical direction in FIG. 1, a larger area may be allotted for each ofthe capacitors 3, and a wider margin may be taken for the positioning ofthe capacitors 3 with the capacitor connection member CC, thus resultingin suppressing defects which would possibly occur in these portions.

Third, by positioning the bit line connection member BC at a cornerportion of the capacitor 3 (a portion of the capacitor 3 opposite to aside of the bit line connection member BC) which would otherwise beremoved during the pattern formation process, the area for the memorycell array M can be effectively utilized.

With these effects in combination, the area of each capacitor 3 can beextended without incurring a significant increase in the entire area ofthe memory cell array M.

Next, a cross-sectional view of the memory cell array M of FIG. 1 takenalong line IIA--IIA and a partial sectional view of a peripheral circuitregion are shown in FIGS. 2A and 3, respectively. Reference is also madeto FIG. 75 which shows a circuit connection diagram for the memory cellarray M.

The semiconductor substrate 1 is made of, for example, p-type silicon(Si) monocrystal. In the semiconductor substrate 1, a p-well 4p isformed in the memory cell array M and a peripheral circuit region A. Thep-well 4p is doped with p-type impurities, for example, boron. Also, inthe semiconductor substrate 1, an n-well 4n is formed in the peripheralcircuit region A. The n-well 4n is doped with n-type impurities, forexample, phosphorus.

The p-well 4p is formed with a channel stopper layer 5p of, for example,p-type. This channel stopper layer 5p is doped with p-type impurities,for example, boron. On the other hand, the n-well is formed with achannel stopper layer 5n of, for example, n-type. This channel stopperlayer 5n is doped with n-type impurities, for example, phosphorus.

On the channel stopper layer 5p within the p-well 4p, a p-typesemiconductor region 7p is formed in an element forming region 6bsurrounded by a field insulating film 6a. This semiconductor region 7pis doped with p-type impurities, for example, boron.

Also, on the channel stopper layer 5n within the n-well 4n, an n-typesemiconductor region 7n is formed in an element forming region 6bsurrounded by the field insulating film 6a. This semiconductor region 7nis doped with n-type impurities, for example, phosphorus. Incidentally,the field insulating film 6a is made of, for example, silicon dioxide(SiO₂).

Formed at the p-type semiconductor region 7p in the memory cell array Mare nMOS's 2 and capacitors 3 each constituting the memory cell MC.

The nMOS 2 has an LDD (Lightly Doped Drain) structure, and isspecifically constituted of a pair of semiconductor regions 2a formed inthe semiconductor region 7p, a gate insulating film 2b formed over thesemiconductor substrate 1, and the gate electrode 2g formed on the gateinsulating film 2b.

The pair of semiconductor regions 2a are provided for constituting asource and a drain of the nMOS 2. Each of the semiconductor regions 2acomprises an n⁻ -type semiconductor region 2a1 formed near the gateelectrode 2g and an n⁺ -type semiconductor region 2a2 formed outsidethereof, both of which are formed by doping, for example, n-typeimpurities such as phosphorus thereinto.

One of the semiconductor regions 2a constituting the nMOS 2 (thesemiconductor region 2a in a central portion of FIG. 2A) for the memorycell MC also serves as one of the semiconductor regions 2a of the nMOS 2for the adjacent memory cell MC. Stated another way, the centralsemiconductor region 2a in FIG. 2 is a common region to the two adjacentmemory cells MC.

The gate insulating film 2b is made of, for example, SiO₂. The gateelectrode 2g, which is part of the word line conductor WL as mentionedabove, is made of, for example, n-type low-resistance polysilicon.Incidentally, an insulating film 9 formed on the side surface of aninsulating film 8 formed on the gate electrode 2g and on the sidesurface of the gate electrode 2g is made of, for example, SiO₂. Also, aside wall 10 formed on the side surfaces of the gate electrode 2g andthe insulating film 8 is an insulating film for forming the LDDstructure, and made of, for example, SiO₂.

A capacitor of a stacked fin structure, for example, is employed as thecapacitor 3. The capacitor 3 is constituted of a capacitor electrode 3a,another capacitor electrode 3b surrounding the capacitor electrode 3a,and a capacitor insulating film 3c formed between the capacitorelectrodes 3a and 3b.

The capacitor electrode 3a, which is made of, for example,low-resistance polysilicon, has, for example, three fins 3a1-3a3. Thiscapacitor electrode 3a is electrically connected to the semiconductorregion 2a of the nMOS 2 through a contact hole 12a formed through aninsulating film 11a (first insulating film) over the semiconductorsubstrate 1.

The other capacitor electrode 3b, which is made of, for example, n-typelow-resistance polysilicon, is electrically connected with a poweringconductor, as will be later described, and set at a predeterminedpotential. The capacitor insulating film 3c in turn is made of, forexample, silicon nitride (Si₃ N₄) or constituted of a laminationincluding a Si₃ N₄ layer and a SiO₂ layer. The insulating film 11a ismade of, for example, SiO₂.

Reference is now made to FIG. 75. In FIG. 75, each of the cell pair unitstructures is drawn by one-dot chain lines and surrounded by abroken-line block, or drawn by solid lines and surrounded by abroken-line block. The former represents a unit structure connected andarranged in accordance with the embodiment of the present invention,while the latter represents a unit structure connected and arranged inaccordance with the prior art (see FIG. 74).

Each of the unit structures extends over two adjacent word lineconductors. Considering a single cell pair unit structure arranged underone bit line conductor BL_(i), a word line conductor WL_(j) connected toa control electrode 2g of a transistor T_(2A) included in the unitstructure is also connected to a control electrode 2g of a secondtransistor T_(2B) in a cell pair unit structure arranged under a bitline conductor BL_(i-1) adjacent to the bit line conductor BLi. Anotherword line conductor WL_(j+1) connected to a control electrode 2g of atransistor T_(2B) in a unit structure arranged under the bit lineconductor BL_(i) is also connected to a control electrode 2g of a firsttransistor T_(2A) in a cell pair unit structure arranged under a bitline conductor BL_(i+1) adjacent to the bit line conductor BL_(i).

Referring now to FIG. 3, an nMOS 13 having the LDD structure, forexample, is also formed over the semiconductor substrate 1 in theperipheral circuit region A. The nMOS 13 is constituted of a pair ofsemiconductor regions 13a formed in the semiconductor region 7p, a gateinsulating film 13b formed over the semiconductor substrate 1, and agate electrode 13g formed on the gate insulating film 13b.

The pair of semiconductor regions 13a are provided for constitutingsource and drain regions for the nMOS 13, wherein each of thesemiconductor regions 13a comprises an n⁻ -type semiconductor region13a1 formed near the gate electrode 13g and an n⁺ -type semiconductorregion 13a2 formed outside thereof. The n⁻ -type semiconductor region13a1 is doped with n-type impurities, for example, phosphorus, while then⁺ -type semiconductor region 13a2 is doped with n-type impurities, forexample, arsenic (As).

A pMOS 14 having the LDD structure, for example, is also formed over thesemiconductor substrate 1 in the peripheral circuit region A. The pMOS14 is constituted of a pair of semiconductor regions 14a formed withinthe semiconductor region 7n, a gate insulating film 14b formed over thesemiconductor substrate 1, and a gate electrode 14g formed on the gateinsulating film 14b.

The pair of semiconductor regions 14a are provided for constitutingsource and drain regions for the pMOS 14. Each of the semiconductorregions 14a comprises a p⁻ -type semiconductor region 14a1 arranged nearthe gate electrode 14g and a p⁺ -type semiconductor region 14a2 arrangedoutside thereof, both of which are formed by doping, for example, p-typeimpurities such as boron thereinto.

Incidentally, the gate insulating films 13b, 14b of the nMOS 13 and thepMOS 14 are made of, for example, SiO₂, while the gate electrodes 13g,14g are made of, for example, n-type low-resistance polysilicon.

Referring again to FIG. 2A, together with FIG. 3, on the insulating film11a, an insulating film (first insulating film) 11b made of, forexample, SiO₂ is deposited so as to cover the capacitors 3, the nMOS's13 and the pMOS's 14. Also, an insulating film (first insulating film)11c made of, for example, SiO₂ is deposited on the insulating film 11b.Further, an insulating film (first insulating film) 11d made of, forexample, SiO₂ is deposited on the insulating film 11c.

The bit line conductors BL are formed on the insulating film 11d. Eachof the bit line conductors BL is electrically connected to thesemiconductor region 2a of the nMOS 2 through a bit line connectionmember BC in a contact hole (first contact hole) 12b formed through theinsulating films 11a-11d. In Embodiment 1, the contact hole 12b isfilled with, for example, n-type low-resistance polysilicon.

With the prior art technique for filling the contact hole 12b only withmetal, if the contact hole 12b were shifted, the filled metal wouldextend over both the semiconductor region 2a and the semiconductorsubstrate 1 at the bottom end of the contact hole 12b, resulting inoccasionally short-circuiting the semiconductor region 2a with thesemiconductor substrate 1.

Also, if a metal is used as a filling material, impurities cannot bediffused into the lightly doped semiconductor region, so that thecontact resistance for the semiconductor region cannot be decreased.

As a prior art method for avoiding these problems, a technique has beenproposed to form bit line conductors of polycide. However, in this case,since wiring conductors for connection between nMOS's and pMOS's existin a peripheral circuit region, the bit line conductors BL cannot beused as wiring conductors for the peripheral circuit region.

In Embodiment 1, since the contact hole 12b is filled withlow-resistance polysilicon, this structure is free from the problem ofshort-circuiting due to the above-mentioned shifted bit line conductorsBL, the problem of the contact resistance between the bit line conductorBL and the semiconductor region 2a, and so on. In addition, thisstructure enables first level wiring conductors 15a for the peripheralcircuit region to be formed on the same layer as the bit line conductorsBL, using the same metal film for providing the bit line conductors BL.

The above features of Embodiment 1 leads to reducing a region forforming a sense amplifier circuit which is an element in the peripheralcircuit region. This reduction is accomplished mainly by the followingreasons:

(1) first, the sense amplifier circuit can be constituted of the firstlevel wiring conductor 15a having a minimum machining dimension rulesimilar to the wiring conductors in the memory cell array M; and

(2) secondly, wiring conductors for the sense amplifier circuit andcolumn selection wiring conductors, which have conventionally beenarranged together at a layer level one level higher than the bit lineconductors BL, can be arranged in separate layer levels. Specifically,in contrast with the prior art in which wiring conductors for the senseamplifier circuit and the column selection wiring conductors had to bearranged in a single wiring layer so that a relatively large area had tobe taken for forming the sense amplifier circuit, Embodiment 1 is freefrom such area restraint.

The first level wiring conductors 15a constituting the peripheralcircuit region are each electrically connected to the semiconductorregion 13a of the nMOS 13 and the semiconductor region 14a of the pMOS14 through a contact hole (second contact hole) 12c formed through theinsulating films 11b-11d.

Also, an insulating film 11e made of, for example, SiO₂ is formed on theinsulating film 11d so as to cover the bit line conductors BL. Then,second layer wiring conductors 15b are formed on the top surface of theinsulating film 11e, and an insulating film 11f is also formed forcovering the second layer wiring conductors 15b.

The second layer wiring conductors 15b are made of, for example,tungsten, and electrically connected to the first level wiringconductors 15a through the contact holes 12d formed through theinsulating film 11e. The insulating film 11f in turn is made of, forexample, SiO₂, and third layer wiring conductors 15c are formed on thetop surface of the insulating film 11f.

The third layer wiring conductors 15c comprise a metal film 15c1 madeof, for example, tungsten, a metal film 15c2 made of, for example,aluminum(Al)--silicon(Si)--copper(Cu) alloy, and a metal film 15c3 madeof, for example, tungsten, which are stacked in this order from thelower layer. The third layer wiring conductors 15c are electricallyconnected to the second layer wiring conductors 15c through contactholes 12e formed through the insulating film 11f.

It should be noted that if it is desired that the second layer wiringconductors 15b are provided with a lower resistance, the second layerwiring conductors 15b may be formed of a metal film similar to the thirdlayer wiring conductors 15c which have a tungsten film, an Al--Si--Cualloy film and a tungsten film stacked in this order.

A surface protection film 16a made of, for example, Si₃ N₄ is formed onthe third layer wiring conductors 15c. Further, on the insulating film11f, a surface protection film 16b is deposited for covering the thirdlayer wiring conductors 15c and the surface protection film 16a. Thissurface protection film 16b is made of, for example, SiO₂.

Next, FIG. 4 shows a plan view of a main portion of a connection areaprovided for connecting the word line conductors WL with the third layerwiring conductors 15c.

This connection area C is arranged such that it is sandwiched betweenadjacent memory array cells M. Each of the third layer wiring conductors15c (see FIGS. 2 and 3) is electrically connected to a rectangularconnection conductor 17 formed on the first level wiring conductor 15a(see FIG. 3) through a contact hole 12f, and is further electricallyconnected to a word line conductor WL through a contact hole 12g whichconnects the connection conductor 17 with the word line conductor WL.Incidentally, the connection conductors 17 are made of, for example,tungsten.

It should be pointed out that in Embodiment 1, the mutually adjacentconnection conductors 17 are spaced by such an interval that allows aword line conductor WL to intervene therebetween. Since this arrangementcan alleviate a spacing required between mutually adjacent connectionconductors 17, a larger positioning margin can be taken for them.

In Embodiment 1, a powering conductor 18 is also arranged on theoutermost side of each memory cell array M. In FIG. 4 the poweringconductors 18 are shown with hatching for facilitating the distinctionthereof from other regions.

The powering conductors 18 are provided for supplying the aforementionedcapacitor electrodes 3b (see FIG. 2) with a predetermined potential, andare arranged on the outermost side of the respective memory cell arraysM in parallel with the bit line conductors BL such that they comply withthe regularity of the repetitive arrangement for the bit line conductorsBL.

This enables an improved reliability of the outermost bit lineconductors BL in the respective memory cell arrays M. This is becausethe powering conductor 18 thus arranged can prevent deformation or thelike of the outermost bit line conductor BL in each memory cell array M,when the pattern of the bit line conductor BL is transferred, whichwould occur unless the wiring conductor 18 were provided.

Each of the powering conductors 18 is provided with powering pads 18aprotruding toward the connection area C at predetermined intervals. Eachof the powering pads 18a has a contact hole 18b formed therein forelectrical connection to the common electrode 3b of the capacitors 3.The powering pads 18a of the two powering conductors 18 extending inparallel with each other are interdigitally arranged with the connectionarea C intervening therebetween. Stated another way, between mutuallyadjacent powering pads 18a of one powering conductor 18, a powering pad18a of the adjacent powering conductor 18 is positioned. In this way,the distance between two adjacent powering conductors 18 can be reducedwhile maintaining an area required for the powering pads 18a.

Next, a manufacturing method of the semiconductor integrated circuitdevice according to Embodiment 1 will be described with reference toFIGS. 5-46. Note that odd-numbered ones among these figures show thememory cell array M, while even-numbered ones show the peripheralcircuit region A.

FIGS. 5 and 6 respectively show a main portion of a semiconductorsubstrate 1 in a manufacturing process for the semiconductor integratedcircuit device according to Embodiment 1.

The semiconductor substrate 1 is formed of, for example, p-type Simonocrystal, on which a p-well 4p and an n-well 4n are formed.

The n-well 4n is formed by providing an ion implanting mask for exposingonly a region for the n-well 4n on the semiconductor substrate 1, thenimplanting n-type impurities such as phosphorus, for example, into thesemiconductor substrate 1 by an ion implanting method, and thenannealing the semiconductor substrate 1.

The p-well 4p in turn is formed by providing an ion implanting mask forexposing only a region for the p-well 4p on the semiconductor substrate1, then implanting, for example, boron fluoride (BF₂) into thesemiconductor substrate 1 by the ion implanting method, and thenannealing the semiconductor substrate 1.

On the top surface of the semiconductor substrate 1, a field insulatingfilm 6a for element separation has already been formed by, for example,a LOCOS (Local Oxidization of Silicon) method. Also, an insulating film19a made of, for example, SiO₂ has already been formed on an elementforming region 6b surrounded by the field insulating film 6a over thesemiconductor substrate 1.

For the semiconductor substrate 1 thus processed, channel stopper layersfor element separation are formed, for example, by the following method.

First, after a photo resist pattern 20a (hereinafter simply called "theresist pattern") for exposing only a region for the p-well 4p is formedover the semiconductor substrate 1 by photolithography techniques,p-type impurities such as boron, for example, are implanted into thesemiconductor substrate 1 by the ion implanting method or the like withthe resist pattern 20a used as an ion implanting mask (FIGS. 5 and 6).

Subsequently, after the resist pattern 20a is removed, a resist pattern20b for exposing only a region for the n-well 4n is formed over thesemiconductor substrate 1 by the photolithography techniques as shown inFIGS. 7 and 8.

Thereafter, n-type impurities such as phosphorus, for example, areimplanted into the semiconductor substrate 1 by the ion implantingmethod or the like with the resist pattern 20b used as an ion implantingmask (FIGS. 7 and 8), and then the resist pattern 20b is removed.

After the resist pattern 20b is removed, the semiconductor substrate 1is annealed in an atmosphere of a mixed gas consisting of nitrogen (N₂),as a principal component, and oxygen (O₂) to form channel stopper layers5p, 5n over the semiconductor substrate 1, as shown in FIGS. 9 and 10.

It should be noted that in Embodiment 1, the channel stopper layers 5p,5n are formed by the ion implanting method or the like after forming thefield insulating film 6a. By thus forming the channel stopper layers 5p,5n, the following effects can be produced.

First, since the channel stopper layers 5p, 5n are formed by the ionimplanting method, which provides a high formation controllability, theformed positions, impurity concentrations, and so on thereof arefavorably controlled.

Secondly, the method of forming the channel stopper layers according tothis embodiment can prevent a narrow channel effect which would occur ifa prior art method were used to form channel stopper layers beforeforming the field insulating film 6a. Therefore, the MOS's constitutingmemory cells can be made finer. The narrow channel effect in this caseis a phenomenon which is caused by impurities for the channel stopperlayers diffusing toward the channel.

Embodiment 1 can prevent the narrow channel effect by the followingreason, in addition to the fact that a good formation controllability isprovided because the ion implanting method is used to form the channelstopper layers 5p, 5n. That is, in Embodiment 1, since impurity ions areimplanted for the channel stoppers after the field insulating film 6a isformed, the impurity ions are implanted into a region deeper than thelocation of the field insulating film 6a, and consequently the impurityions are hardly diffused toward the channel.

Additionally, in Embodiment 1, since the channel stopper layers 5p, 5nare formed also for the peripheral circuit region A by the method asdescribed above, the following effects can be produced.

First, since the narrow channel effect can be prevented also in theMOS's in the peripheral circuit region A, the MOS's in the peripheralcircuit region A can be made finer. That is, Embodiment 1 can respond tothe requirement of a finer structure of the peripheral circuit region A.

Secondly, since the channel stopper layers 5p, 5n are formedsimultaneously with the formation of the channel stopper layers 5p, 5nin the memory cell array M, the number of exposure masks and the numberof manufacturing processes can be reduced.

Next, a basic structure of the MOS.ET is formed over the semiconductorintegrated circuit 1, for example, by the following method.

First, as shown in FIGS. 11 and 12, predetermined impurities areimplanted into respective element forming regions 6b surrounded by thefield insulating film 6a over the semiconductor substrate 1 by the ionimplanting method or the like to form p-type and n-type semiconductorregions 7p, 7n, so as to provide the electric characteristics requiredfor elements to be formed in the associated element forming regions.

Subsequently, after insulating films (not shown) formed on the elementforming regions 6b are removed to expose the surface of thesemiconductor substrate 1, the semiconductor substrate 1 is subjected tothermal oxidization processing or the like to form a gate insulatingfilm 21 on the exposed surface of the semiconductor substrate 1.

After the formation of the gate insulating film 21, a conductive film22a made of, for example, n-type low-resistance polysilicon is depositedover the semiconductor substrate 1 by a CVD method or the like. Areactive gas used in this process may be, for example, a mixed gasconsisting of silane (SiH₄) and phosphine (PH₃).

Next, an insulating film 8' made of, for example, SiO₂ is deposited onthe conductive film 22a by the CVD method or the like. A reactive gasused in this process may be, for example, a mixed gas consisting ofnitrogen oxide (N₂ O) and SiH₄.

Subsequently, after a resist pattern (not shown) for forming a gateelectrode is formed on the insulating film 8' by photolithographytechniques, the insulating film 8' is patterned by a dry etching methodor the like with the resist pattern used as an etching mask.

Then, after the resist pattern is removed, the conductive film 22a ispatterned by the dry etching method or the like, with the patternedinsulating film 8' used as an etching mask, to form gate electrodes 2g,13g, 14g, word line conductors WL, and an insulating film 8 over thesemiconductor substrate 1, as shown in FIGS. 13 and 14.

Next, the semiconductor substrate 1 is subjected to light thermaloxidization processing to form insulating films 9 on side surfaces ofthe respective gate electrodes 2g, 13g, 14g.

Subsequently, after forming a resist pattern (not shown) for coveringthe entire surface except for an upper portion of the p-well 4p over thesemiconductor substrate 1 by photolithography techniques, n-typeimpurities such as phosphorus, for example, are implanted into thesemiconductor substrate 1 by the ion implanting method or the like, withthe resist pattern and the gate electrodes 2g, 13g used as ionimplanting masks.

Then, after the resist pattern used in the ion implantation process isremoved, the semiconductor substrate 1 is subjected to a heat treatmentto form n⁻ -type semiconductor regions 2a1, 13a1 within thesemiconductor region 7p.

Next, after forming a resist pattern (not shown) for covering the entiresurface except for an upper portion of the n-well 4n over thesemiconductor substrate 1 by photolithography techniques, p-typeimpurities such as boron, for example, are implanted into thesemiconductor substrate 1 by the ion implanting method or the like, withthe formed resist pattern and the gate electrode 14g used as ionimplanting masks.

Subsequently, after the resist pattern used in the ion implantationprocess is removed, the semiconductor substrate 1 is subjected to a heattreatment to form a p-type semiconductor region 14a1 within thesemiconductor region 7n. In this way, the basic structures of the nMOS's2, 13 and PMOS 14 are formed over the semiconductor substrate 1.

Then, after depositing an insulating film made of, for example, SiO₂over the semiconductor substrate 1 by the CVD method or the like, theinsulating film is etched back to form side walls on side surfaces ofthe gate electrodes 2g, 13g, 14g and the insulating film 8, as shown inFIGS. 15 and 16.

After the formation of the side walls 10, an insulating film 11a madeof, for example, SiO₂ is deposited over the semiconductor substrate 1 bythe CVD method or the like. A reactive gas used in this process may be,for example, a mixed gas consisting of N₂ O and SiH₄.

Next, capacitors constituting the memory cells are formed over thesemiconductor substrate 1, for example, by the following method.

First, as shown in FIGS. 17 and 18, a resist pattern 20c for exposingonly an upper portion of the n⁻ -type semiconductor region 2a1 on theouter side of the nMOS 2 is formed on insulating film 11a by thephotolithography techniques. Then, with the photo resist pattern 20cused as an etching mask, portions of the insulating film 11a, which arenot covered with the resist pattern 20c, are etched away to form contactholes 12a through the insulating film 11a so as to expose portions ofthe n⁻ -type semiconductor region 2a1. After the formation of thecontact holes 12a, the resist pattern 20c is removed.

Subsequently, as shown in FIGS. 19 and 20, a conductive film (firstconductive film) 22b made of, for example, n-type low-resistancepolysilicon is deposited over the semiconductor substrate 1 by the CVDmethod or the like. A reactive gas used in this process may be, forexample, a mixed gas consisting of silane (SiH₄) and PH₃.

The semiconductor substrate 1 is annealed, for example, in a N₂ gasatmosphere, so that the n-type impurity in the conductive film 22b isdiffused into the substrate 1 to form an n⁺ -type semiconductor region2a2.

After the deposition of the conductive film 22b, a resist pattern 20dfor covering only capacitor forming regions is formed on the conductivefilm 22b by photolithography techniques. Then, with the resist pattern20d used as an etching mask, the conductive film 22b is patterned by thedry etching method or the like to form a first fin 3a1 for eachcapacitor electrode 3a, as shown in FIGS. 21 and 22.

Next, an insulating film 23a made of, for example, Si₃ N₄ is depositedover the semiconductor substrate 1 by the CVD method or the like. Areactive gas used in this process may be, for example, a mixed gasconsisting of silane dichloride (SiH₂ Cl₂) and ammonia (NH₃).

Subsequent to the deposition of the insulating film 23a, an insulatingfilm 24a made of, for example, SiO₂ is deposited on this insulating film23a by the CVD method or the like. A reactive gas used in this processmay be, for example, a mixed gas consisting of SiH₄ and

Thereafter, an insulating film 24b made of, for example, BPSG (BoroPhospho Silicate Glass) is deposited on the insulating film 24a by theCVD method or the like. A reactive gas used in this process may be, forexample, a mixed gas composed of TEOS (Tetraethoxysilane) and O₂ withpredetermined amounts of boron and phosphorus added thereto.

The insulating films 23a, 24a and 24b serve as an insulating base filmfor conductive films for forming second and third fins 3a2 and 3a3.

Next, the semiconductor substrate 1 with the films formed thereon isannealed, for example, in an atmosphere of a mixed gas consisting of N₂and O₂ to flatten the top surface of the insulating film 24b, as shownin FIGS. 23 and 24.

Subsequently, after etching back an upper portion of the insulating film24b, the semiconductor substrate 1 with the films formed thereon isannealed, for example, in an atmosphere of a mixed gas consisting of N₂and O₂ to further flatten the top surface of the insulating film 24, asshown in FIGS. 25 and 26.

Stated another way, in Embodiment 1, after the first fin 3a1 is formedfor the capacitor 3 (see FIG. 2), the top surface of the insulating film24b is flattened to serve as a good base for second and third fins 3a2,3a3 for the capacitor 3.

In this way, the conductive films for forming the second and third fins3a2, 3a3 can be made planar. This results in producing, for example, thefollowing effects.

First, defective formation of the second and third fins 3a2, 3a3, causedby an uneven base, can be suppressed.

Secondly, the conductive films will not be over-etched when forming thesecond and third fins 3a2, 3a3.

Thirdly, since the conductive films can be formed into the second andthird fins 3a2, 3a3 with an improved pattern machining accuracy, apattern dimension accuracy can also be improved for the fins 3a2, 3a3.

Also, since the conductive films for forming the second and third finsare made planar, a capacitor insulating film can be made thinner. Withsuch a thinner insulating film, the storage capacitance of the capacitorcan be increased.

The flattening technique as described above becomes increasinglyeffective and important for ensuring the reliability of the capacitors 3as the number of fins constituting the capacitors 3 is increased.

Next, an insulating film (third insulating film) 24c made of, forexample, SiO₂ is deposited on the top surface of the flattenedinsulating film 24b by the CVD method or the like. A reactive gas usedin this process may be, for example, a TEOS gas.

Subsequently, a conductive film (second conductive film) 22c made of,for example, n-type low-resistance polysilicon is deposited on theinsulating film 24c by the CVD method or the like. A reactive gas usedin this process may be, for example, a mixed gas consisting of silane(SiH₄) and PH₃. It should be noted that the conductive film 22c isprovided for forming the second fin 3a2 for each capacitor 3.

Thereafter, an insulating film (third insulating film) 24d made of, forexample, SiO₂ is deposited on the conductive film 22c by the CVD methodor the like. A reactive gas used in this process may be, for example, amixed gas consisting of SiH₄ and N₂ O.

Next, as shown in FIGS. 27 and 28, a resist pattern 20e for exposingonly an upper portion of a central region on the top surface of the fin3a1 is formed on the insulating film 24d by photolithography techniques.

Subsequent to the formation of the resist pattern 20e, a contact hole12f is formed through the conductive film 22c and the insulating film23a, 24a-24d by a dry etching method or the like, with the resistpattern 20e used as an etching mask, so as to expose a central portionof the top surface of the fin 3a1. Then, the resist pattern 20e isremoved.

Thereafter, as shown in FIGS. 29 and 30, a conductive film (secondconductive film) 22d made of, for example, n-type low-resistancepolysilicon is deposited over the semiconductor substrate 1 by the CVDmethod or the like. A reactive gas used in this process may be, forexample, a mixed gas consisting of SiH₄ and PH₃. It should be noted thatthe conductive film 22d is provided for forming the third fin 3a3 forthe capacitor 3.

Next, after forming a resist pattern 20f for forming the capacitors onthe conductive film 22d by photolithography techniques, portions of theconductive film 22c and the insulating film 24d, which are not coveredwith the resist pattern 20f, are removed by the dry etching method orthe like, with the resist pattern 20f used as an etching mask.

By patterning the conductive films 22c, 22d and the insulating film 24din this way, the second and third fins 3a2, 3a3 are formed to completeeach capacitor electrode 3a, as shown in FIGS. 31 and 32.

Subsequently, after removing the resist pattern 20f, the insulatingfilms 24a-24c are removed by a wet etching method or the like. Then, theinsulating film 23a is removed by using, for example, hot phosphoricacid or the like to expose the surfaces of the capacitor electrodes 3a.

After removing the insulating film 23a, an insulating film 23b made of,for example, Si₃ N₄ is deposited on the surfaces of the capacitorelectrodes 3a and the insulating film 11a by the CVD method or the like,as shown in FIGS. 33 and 34. A reactive gas used in this process may be,for example, a mixed gas consisting of SiH₂ Cl₂ and NH₃.

Next, the surface of the insulating film 23b is oxidized in anatmosphere of a mixed gas consisting of, for example, O₂ and hydrogen(H₂), and then a conductive film 22d made of, for example, n-typelow-resistance polysilicon is formed on the insulating film 23b by theCVD method or the like. A reactive gas used in this process may be, forexample, a mixed gas consisting of SiH₄ and PH₃.

Subsequently, the conductive film 22d is patterned by photo resisttechniques to form capacitor electrodes 3b, thus completing thecapacitors 3, as shown in FIG. 35.

After the capacitors 3 are made, an insulating film 11b is formed overthe semiconductor substrate 1 by the CVD method or the like, as shown inFIGS. 35 and 36. reactive gas used in this process may be, for example,a TEOS gas.

Next, after forming a resist pattern (not shown) for covering the entiresurface except for an upper portion of the nMOS region in the peripheralcircuit region on the insulating film 11b, n-type impurities such as As,for example, are doped into the semiconductor region 7p with the newlyformed resist pattern and the gate electrode 13g of the nMOS 13 used asion implanting masks.

Subsequent to the As doping process, the resist pattern is removed.Then, a resist pattern (not shown) for covering the entire surfaceexcept for an upper portion of the pMOS region in the peripheral circuitregion is formed on the insulating film 11b. This resist pattern and thegate electrode 14g of the pMOS 14 are used as ion implanting masks todope p-type impurities such as boron, for example, into thesemiconductor region 7n.

Then, after removing the resist pattern, the semiconductor substrate 1with the films so far formed thereon is annealed in a N₂ gas atmosphereto form an n⁺ -type semiconductor region 13a2 for the nMOS 13 and a p⁺-type semiconductor region 14a2 for the PMOS 14, thus completing the LDDstructure of the NMOS 13 and the PMOS 14 in the peripheral circuitregion.

Next, bit line conductors are formed over the semiconductor integratedcircuit 1, for example, by the following method.

First, an insulating film 11c made of, for example, SiO₂ is deposited onthe insulating film 11b by the CVD method or the like. A reactive gasused in this process may be, for example, a mixed gas consisting of SiH₄and N₂ O.

Subsequently, an insulating film 11d made of, for example, BPSG isdeposited on the insulating film 11c by the CVD method or the like. Areactive gas used in this process may be a mixed gas composed of a TEOSgas with phosphorus and boron added thereto.

Then, after the semiconductor substrate 1 with the films so far formedthereon is annealed in an atmosphere of a mixed gas, for example,consisting of N₂ and O₂ to flatten the top surface of the insulatingfilm 11d, an upper portion of the insulating film 11d is etched back,and the semiconductor substrate 1 with the films so far formed thereonis again annealed to flatten the top surface of the insulating film 11d,as shown in FIGS. 37 and 38.

Next, after forming a contact hole 12b through the insulating film 11dso as to expose the top surface of a portion of the n⁻ -typesemiconductor region 2a1 in the nMOS 2 by photolithography techniques, aconductive film 22e made of, for example, n-type low-resistancepolysilicon doped with a high concentration of n-type impurity (e.g.,phosphorus) is deposited on the insulating film 11d. A reactive gas usedin this process may be, for example, a mixed gas consisting of SiH₄ andPH₃.

Subsequent to the formation of the contact hole 12b, an upper portion ofthe conductive film 22e is etched back so as to fill the conductive film22e only in the contact hole 12b, as shown in FIG. 39. The filledconductive film 22e forms part of the bit line connection member BC.

The semiconductor substrate 1 is annealed, for example, in a N₂ gasatmosphere, so that the n-type impurity in the filled conductive film22e is diffused into the substrate 1 to form another n⁺ -typesemiconductor region 2a2.

Thereafter, as shown in FIGS. 39 and 40, a resist pattern 20g is formedon the insulating film 11d by photolithography techniques for exposingonly upper portions of one n⁺ -type semiconductor region 13a2 of thenMOS 13 and one p⁺ -type semiconductor region 14a2 of the pMOS 14 in theperipheral circuit region. Then, with the resist pattern 20g used as anetching mask, contact holes 12c are formed through the insulating film11d for exposing the semiconductor regions 13a2, 14a2.

Next, after removing the resist pattern 20g, a metal film 25a made of,for example, tungsten is formed over the semiconductor substrate 1 asshown in FIGS. 41 and 42.

The metal film 25a is formed by first depositing a metal film made oftungsten or the like over the semiconductor substrate 1 by a sputteringmethod, the CVD method or the like and then depositing a metal film madeof tungsten or the like on the metal film by the CVD method or the like.A reactive gas used in the CVD processing may be, for example, a mixedgas consisting of tungsten hexafluoride (WF₆) and H₂.

Subsequent to the formation of the metal film 25a, the metal film 25a ispatterned by normal photolithography techniques to form bit lineconductors BL for constituting memory circuits over the semiconductorsubstrate 1, and simultaneously with this patterning, first level wiringconductors 15a are patterned for constituting peripheral circuits.

Briefly, in Embodiment 1, the metal film 25a for constituting the bitline conductors BL is used to also form the first level wiringconductors 15a for constituting the peripheral circuits on the samelayer level as the bit line conductors BL. As a result, the followingeffects are produced.

First, since the contact holes 12c of substantially a uniform depth canbe provided for connecting the first level wiring conductors 15a withthe nMOS 13 and the pMOS 14, the reliability of the contact therebetweencan be improved.

Conventionally, the depths of contact holes for connecting the firstlevel wiring conductors for peripheral circuits with elements in theperipheral circuit region have not been uniformly formed, for example,for the following reasons. Since wiring conductors for peripheralcircuits are conventionally formed in a layer higher than a layer inwhich bit line conductors are formed, an extra layer formed of aninsulating film intervenes between the wiring conductors for peripheralcircuits and the elements. Thus, possible variations in the thickness ofthe intervening insulating film also result in varying the depths ofrespective contact holes 12c extending from the wiring layer on theinsulating film to the elements.

Secondly, since the wiring layer for the bit line conductors BL may beused as a wiring layer for the first level wiring conductors 15a, thefreedom in arrangement of wiring conductors can be improved.

Next, second level wiring conductors and third level wiring conductorsare formed over the semiconductor substrate 1, for example, by thefollowing method.

First, as shown in FIGS. 43 and 44, an insulating film 11e is formed onthe insulating film 11d so as to cover the bit line conductors BL andthe first level wiring conductors 15a. The insulating film 11e isformed, for example, in the following manner.

An insulating film made of, for example, SiO₂ is initially deposited onthe insulating film 11d by the CVD method or the like using, forexample, a mixed gas consisting of TEOS, helium (He) and O₂, and then anSOG (Spin On Glass) film, for example, is coated on the insulating film.

Subsequently, an upper portion of the two-layer structured insulatingfilm is etched back to flatten the top surface thereof, and thereafteran insulating film made of, for example, SiO₂ is deposited on theinsulating film by the CVD method or the like using, for example, amixed gas consisting of TEOS and O₂, thus completing the formation ofthe insulating film 11e.

Next, after forming the insulating film 11e, contact holes 12d areformed through the insulating film 11e in the peripheral circuit regionA so as to expose portions of the first level wiring conductors 15a.Then, the second level wiring conductors 15b are formed on theinsulating film 11e a manner similar to the first level wiringconductors 15a.

Subsequent to the formation of the second level wiring conductors 15b,an insulating film 11f is formed on the wiring conductors 15b. Thisinsulating film 11f may also be formed, for example, in a manner similarto the insulating film 11e.

Thereafter, as shown in FIGS. 45 and 46, contact holes 12e are formedthrough the insulating film 11f in the peripheral circuit region A so asto expose portions of the second level wiring conductors 15b. Then, ametal film 25b is formed on the insulating film 11f, for example, in thefollowing manner.

First, a metal film made of, for example, tungsten is deposited on theinsulating film 11f, for example, by the sputtering method, the CVDmethod or the like. Then, a metal film made of tungsten or the like isdeposited on the metal film by a blanket CVD method to form a metal film25bl. A reactive gas used for the blanket CVD processing may be, forexample, a mixed gas consisting of WF₆ and H₂.

Subsequently, a metal film 25b2 made of, for example, Al--Cu--Si alloyis deposited on the metal film 25b1 by the sputtering method or thelike. Further, on the metal film 25b2, a metal film 25b3 made of, forexample, tungsten is deposited by a sputtering method or the like, thuscompleting the metal film 25b.

After the formation of the metal film 25b, an insulating film 23c madeof, for example, Si₃ N₄ is deposited on the metal film 25b3 by the CVDmethod or the like. A reactive gas used in this process may be, forexample, a mixed gas consisting of SiH₄, NH₃ and N₂.

Thereafter, the metal film 25b and the insulating film 23c are patternedby normal photolithography techniques to form the third level wiringconductors 15c and a surface protection film 16a, as shown in FIGS. 2and 3.

After forming the third level wiring conductors 15c, a surfaceprotection film 16b made of, for example, SiO₂ is formed on theinsulating film 11f by the CVD method or the like so as to cover thethird level wiring conductors 15c. A reactive gas used in this processmay be, for example, a mixed gas consisting of TEOS, He and O₂.

According to Embodiment 1 as described above, the following effects canbe produced.

(1) The cell pair unit structure having a bit line connection member BCand two memory cells MC arranged on both sides of the bit lineconnection member BC are positionally shifted in the right direction inFIG. 1 by a quarter of the periodic pattern each time the bit lineconductor BL is repetitively arranged in the downward direction in FIG.1, so that the capacitors 3 are not sequentially arranged along thevertical direction in FIG. 1. Thus, the distance between adjacentcapacitors 3 in the vertical direction in FIG. 1 can be made longer, anda positioning margin between the capacitors and the capacitor connectionmember CC can be made wider.

(2) By positioning the bit line connection member BC at a corner portionof the capacitor 3 (a portion of the capacitor 3 opposite to a side ofthe bit line connection member BC) which would otherwise be removedduring the pattern formation, the area for the memory cell array M canbe effectively utilized.

(3) With the effects (1) and (2), the area of each capacitor 3 can beextended without incurring a significant increase in the entire area ofthe memory cell array M.

(4) Since the contact holes 12b, through which the bit line conductorsBL are connected to the semiconductor region 2a of the nMOS 2 in thememory cell MC, are filled with, for example, low-resistancepoly-silicon, this structure is free from the problem ofshort-circuiting due to a shifted bit line conductor BL, the problem ofthe contact resistance between the bit line conductor BL and thesemiconductor region 2a, and so on. In addition, this structure enablesthe first level wiring conductors 15a for peripheral circuits to beformed on the same layer level as the bit line conductors BL, by using ametal film for providing the bit line conductors BL.

(5) The above effect (4) also contributes to the formation of a uniformdepth for the contact holes 12c each for connecting the first levelwiring conductor 15a to the nMOS 13 or the pMOS 14 in the peripheralcircuit region A, whereby the reliability of the connection madetherethrough can be improved.

(6) Since the effect (4) also allows the wiring layer for the bit lineconductors BL, which has conventionally not been able to be used forwiring conductors constituting peripheral circuits, to be used as awiring layer for the first level wiring conductors 15a constitutingperipheral circuits, a region for arranging wiring conductors can beextended. In this way, the peripheral circuit region A can be reduced.Also, a freedom in arranging wiring conductors in the peripheral circuitregion a can be improved.

(7) In the connection area C (FIG. 4) for connecting the third levelwiring conductors 15c to the word line conductors WL, mutually adjacentconnection conductors 17 are separated by such a spacing that allows oneword line conductor WL to intervene therebetween, so that a wiringspacing required between the mutually adjacent connection conductors 17can be alleviated, thus making it possible to provide a largerpositioning margin as well as to reduce the connection area C.

(8) By arranging-the powering conductor 18 on the outermost side of eachmemory cell array M in parallel with the bit line conductors BL suchthat it complies with the regularity of the repetitive arrangements forthe bit line conductors BL, the powering conductor 18 can preventthinning of the outermost bit line conductor BL in each memory cellarray M which would occur if such a wiring conductor 18 were notprovided, thus improving the reliability of the outermost bit lineconductors BL in the respective memory cell arrays M. This effectfurther leads to improving the yield rate and reliability ofsemiconductor integrated circuit devices.

(9) Since the channel stopper layers 5p, 5n are formed using an ionimplanting method or the like after forming the field insulating film 6,good channel stopper layers 5p, 5n can be formed without giving rise tothe narrow channel effect in the nMOS 2 constituting the memory cell MC.It is therefore possible to make the nMOS 2 constituting the memory cellMC in a fine structure.

(10) Since the channel stopper layers 5p, 5n are also formed for theperipheral circuit region A using a method as described above, thenarrow channel effect can be prevented also in the nMOS 13 and the pMOS14 in the peripheral circuit region A, so that the nMOS 13 and the pMOS14 can also be made fine. Stated another way, this formation of thechannel stopper layers can respond to requirements for a fine structureof the peripheral circuit region A.

(11) Since the channel stopper layers 5p, 5n are formed in theperipheral circuit region A simultaneously with the formation of thechannel stopper layers 5p, 5n in the memory cell array M, the number ofexposure masks and the number of manufacturing processes can be reduced.

(12) Since the effect (10) contributes to preventing the narrow channeleffect in the MOS region or the like in the memory cell array M and theperipheral circuit region A, the yield rate and reliability of thesemiconductor integrated circuit device can be improved.

(13) Since the top surface of the insulating film 24b, which serves asthe base for the second and third fins 3a2, 3a3 for the capacitors 3, isflattened after forming the first fin 3a1 for the capacitors 3, theconductive films 22c, 22d for forming the second and third fins 3a2, 3a3can be made planar, thus making it possible to improve the reliabilityand pattern dimension accuracy of the capacitors 3.

(14) By flattening the top surface of the insulating film 24b, whichserves as the base for the second and third fins 3a2, 3a3 for thecapacitors 3, after forming the first fin 3a1 for the capacitor 3, theconductive films 22c, 22d for forming the second and third fins 3a2, 3a3can be made planar, so that the thickness of the capacitor insulatingfilm 3c can be reduced. The reduced thickness of the insulating film 3cenables the storage capacitance of the capacitor 3 to be increased.

(15) By first forming the first fin 3a1 and later forming the second andthird fins 3a2, 3a3 when forming the fin-shaped capacitors 3, a resistpattern used as an etching mask need not be made thick. Therefore, evenif an exposure apparatus only provides a low resolution, the capacitors3, for example, having three fins 3a1-3a3 can be favorably made.

Turning again to FIG. 1, the unit structures are arranged to formoblique sequence unit structures LLk1, LLk2, . . . , LLk5 substantiallyparallel with each other. The oblique sequences of unit structures SUslope in an upper left to lower right direction. As has been describedwith reference to FIG. 2A, each capacitor 3 in each of the unitstructures has a node electrode 3a provided separately for each memorycell, a plate electrode 3b provided in common to plural memory cells anda dielectric film 3c sandwiched therebetween. The distance d1 betweenthe node electrode 3a of the first capacitor 3 of any one of the unitstructures SU in any one oblique sequence (e.g., LLk3) and that of thesecond capacitor 3 of a unit structure SU in an oblique sequence (e.g.,LLk2) adjacent to the first-mentioned oblique sequence is determined ordefined by delineation limits or minimal lithography sizes. In otherwords, the distances dl between the node electrodes 3a of the capacitors3 of the unit structures in adjacent two oblique sequences as viewed ina direction perpendicular to the sloping direction of the obliquesequences are determined or defined by delineation limits or minimallithography sizes.

In FIG. 1, the switching transistors of adjacent two memory cells areformed in an elongated element forming region 6b which is surrounded byfield insulating films 6a (FIG. 2A). All of the elongated elementforming regions 6b are sloped in the same direction relative to the bitline conductors BL such that the longitudinal direction thereof is notin parallel with the extending (lengthwise) direction of the bit lineconductors BL. The element forming region 6b is included in theabove-mentioned memory cell pair unit structure. The element formingregions 6b are sloped in order to prevent the bit line connectionmembers BC of the memory cell pair unit structures, formed under thelayer in which the bit line conductors BL exist, from being formedunnecessarily close to switching transistors of the memory cell pairunit structures formed under the adjacent bit line conductors due tomis-alignment.

Referring next to FIG. 2B showing a cross-sectional view taken alongline IIB--IIB in FIG. 1, which is similar to FIG. 2A, a variety of filmsand the like formed over the insulating film 11e are however omitted forsimplicity sake. Considering that the mask is displaced, due tomis-alignment, from an originally defined position for forming contactholes for connecting two switching transistors constituting two memorycells in each memory cell pair unit structure to the three semiconductorregions 2a1, as will be understood also from FIG. 17, contact holes 12aeach for providing a contact (capacitor connection member CC) to thesemiconductor region 2a1 which is connected with the capacitor 3 areonly formed through the single insulating film 11a (for example, a SiO₂film having a thickness of approximately 100 nm), so that there islittle possibility that the field insulating film 6 be excessivelyremoved by more than an allowable limit.

On the other hand, the contact holes 12b, each for providing a contactto the semiconductor region 2a1 which is connected to the bit lineconnection member BC (n-type polysilicon film 22e in Embodiment 1) forconnection with the bit line conductor BL, are formed through threelayers (having a thickness of approximately 700 nm) including the etchedback insulating film 11d (for example, a BPSG film having a thickness ofapproximately 500 nm), the insulating film 11c (for example, a SiO₂ filmhaving a thickness of approximately 100 nm), and the insulating film 11a(a SiO₂ film having a thickness of approximately 100 nm, as mentionedabove) (FIG. 35), so that it is possible that the field insulating film6 for one of the semiconductor regions 2a1 be removed by more than anallowable limit. If the field insulating film 6 were excessivelyremoved, the bit line connection member BC would be formed unnecessarilytoo close to the semiconductor region 2a1 of the transistor which isconnected to the capacitor in the memory cell pair unit structure formedunder a bit line conductor adjacent to the bit line connection member BC(on the right or left side on FIG. 2B). The bit line connection memberBC thus formed would result in incomplete separation or isolationbetween the bit line connection member BC placed under a bit lineconductor and the capacitor connection member CC placed under a bit lineconductor adjacent to that bit line conductor, thus causing an undesiredleak current to flow therebetween. As a result, defective memory cellswould be manufactured.

To solve this problem, all of the elongated element forming regions 6bare sloped in the same direction relative to the bit line conductors BLso as to prevent the longitudinal direction thereof from coinciding withthe extending (lengthwise) direction of the bit line conductors. In FIG.1, the sloping direction of each element forming region 6b is definedsuch that a left side portion of the element forming region 6b from thebit line connection member BC, which is placed, for example, under thebit line conductor BL (though it is not necessarily placed there), isdirected upwardly relative to the center line of the bit line conductor,and a right side portion of same is directed upwardly relative to thecenter line of the bit line conductor (the element forming region 6b asa whole is rising toward the right), when viewed in FIG. 1. By thuspositioning the semiconductor regions 7p, a wider spacing can beprovided between the bit line connection member BC of a memory cell pairunit structure formed under a bit line conductor and the capacitorconnection member CC for a switching transistor in a memory cell pairunit structure formed under the adjacent bit line conductor, so thateven if the positions of the contact holes are shifted, due to a maskdisplacement, from originally designed positions at which they wouldhave been formed, the structure is free from the above-mentionedincomplete separation or isolation between the bit line connectionmember BC and the adjacent capacitor connection member CC, thus makingit possible to effectively prevent an undesired leak current fromflowing therebetween.

Further, the elongated unit structures or element forming regions 6bformed under the bit line conductors BL and sloped thereto as mentionedabove are arranged in the following manner. Namely, the distance d21between the node electrode 3a of a first one of the capacitors 3 of asloped unit structure formed under a bit line conductor and that of afirst one of the capacitors 3 of a sloped unit structure formed under abit line conductor adjacent to the first-mentioned bit line conductor isdetermined or defined by delineation limits or minimal lithographysizes. And, the distance d22 between the node electrode 3a of a secondone of the capacitors 3 of a sloped unit structure formed under a bitline conductor and that of a second one of the capacitors 3 of a slopedunit structure formed under a bit line conductor adjacent to thefirst-mentioned bit line conductor is determined or defined bydelineation limits or minimal lithography sizes.

The above-described distances d1, d21 and d22 are substantially equal toeach other. The term "delineation limits" or "minimal lithography sizes"is intended to indicate a limit or a size corresponding to a minimumwiring conductor width or minimum space between two wiring conductorsformed in a predetermined conductor layer in a semiconductor chip.

(Embodiment 2)

FIGS. 47-56 are cross-sectional views showing main portions of asemiconductor substrate in manufacturing processes for a semiconductorintegrated circuit device according to another embodiment of the presentinvention.

Embodiment 2 differs from Embodiment 1 in the method of forming thecapacitors which constitute memory cells. This method is carried out,for example, in the following processes. It should be noted that forclarity of the drawings, the drawings used for illustrating Embodiment 2omit the insulating film 9 formed on the side surface of the gateelectrode 2g which is shown in FIG. 2.

FIG. 47 is a cross-sectional view showing a main portion of a memorycell array M in a manufacturing, process for the semiconductorintegrated circuit device according to Embodiment 2, which illustrates astructure similar to that created at the manufacturing process shown inFIG. 13 of Embodiment 1. In an element forming region of a semiconductorsubstrate 1-2, a basic structure of nMOS 2-2 has already been formed.

After an insulating film 24e-2 made of, for example, SiO₂ is firstformed over the semiconductor substrate 1-2 by the CVD method or thelike, as shown in FIG. 48, an insulating film (for protection) 23d-2made of, for example, Si₃ N₄ is deposited on the insulating film 24e-2by the CVD method or the like. Furthermore, an insulating film (secondinsulating film) 24f-2 made of, for example, SiO₂, which has a differentetching rate from the insulating film 23d-2, is deposited on theprotective insulating film 23d-2 by the CVD method or the like.

Subsequently, as shown in FIG. 49, contact holes 12-2 are formed throughthe insulating films 23d-2, 24e-2, 24f-2 by photolithography techniquesfor exposing portions of an n⁻ -type semiconductor region 2a1-2 of thenMOS 2-2.

After the formation of the contact holes 12-2, a conductive film 22f-2made of, for example, n-type low-resistance polysilicon is depositedover the semiconductor substrate 1-2 by the CVD method or the like, asshown in FIG. 50. In Embodiment 2, the conductive film 22f-2 isdeposited in this process to such a degree that the top surface thereofbecomes substantially planar. This conductive film 22f-2 is provided forforming a first fin for capacitors.

Next, the semiconductor substrate 1-2 with the films so far formedthereon is annealed, for example, in a N₂ gas atmosphere to diffusen-type impurities in the conductive film 22f-2 toward the semiconductorsubstrate 1-2 in order to form an n+semiconductor region 2a2-2.

Subsequent to the annealing process, the top surface of the conductivefilm 22f-2 is etched back to further flatten the top surface of theconductive film 22f-2, as shown in FIG. 51.

Then, as shown in FIG. 52, after an insulating film 24g-2 made of, forexample, SiO₂ is deposited on the conductive film 22f-2 by the CVDmethod or the like, a conductive film 22g-2 made of, for example, n-typelow-resistance polysilicon is deposited on the top surface of theinsulating film 24g-2 by the CVD method or the like. Further, aninsulating film 24h-2 made of, for example, SiO₂ is deposited on theconductive film 22g-2 by the CVD method or the like. The conductive film22g-2 is provided for forming a second fin for the capacitors.

Next, as shown in FIG. 53, contact holes 12f-2, each for exposing aportion of the conductive film 22f-2, are formed through the conductivefilm 22g-2 and the insulating films 24g-2, 24h-2 by photolithographytechniques. Then, as shown in FIG. 54, a conductive film 22h-2 made of,for example, n-type low-resistance polysilicon is deposited over thesemiconductor substrate 1-2 by the CVD method or the like. Thisconductive film 22h-2 is provided for forming a third fin for thecapacitors.

Briefly, in Embodiment 2, the top surface of the conductive film 22f-2for forming the first fin for the capacitors is flattened, and on theflattened top surface, the conductive films 22g-2, 22h-2 are depositedfor forming the second and third fins for the capacitors.

By thus forming the structure for the capacitors, the processing forflattening can be easily realized without excessively increasing thenumber of processes, as compared with the processing of flattening theunderlying insulating film prior to the formation of the conductivefilms 22g-2, 22h-2 for providing the second and third fins of thecapacitors.

It is therefore possible to produce effects with respect to thereliability of the capacitors, similar to those of Embodiment 1, in aneasier manner and without excessively increasing the number ofmanufacturing processes.

Subsequent to the deposition of the conductive films 22g-2, 22h-2, aresist pattern 20h-2 for forming capacitors is formed on the conductivefilm 22h-2 by photolithography techniques. Then, with this resistpattern 20h-2 used as an etching mask, the conductive films 22f-2-22h-2and the insulating films 24f-2-24h-2 are patterned to form capacitorelectrodes 3a-2 as well as to expose the surface of the capacitors, asshown in FIG. 55.

It should be noted that in Embodiment 2 the insulating film 23d-2 servesas a protection film having a function of an etching stopper in thepatterning process. With this protection film, the insulating film 24f-2which underlies the first fin 3a1-2, can also be removed when patterningis performed for forming the fins 3a1-2-3a3-2, so that the lower surfaceof the first fin 3a1-2 can also be used as a storage portion of thecapacitor, whereby the capacitance of the capacitor can be increased incomparison with the aforementioned Embodiment 1.

Then, after removing the insulating film 23d-2, for example, by hotphosphoric acid processing or the like, a capacitor electrode 3b-2 and acapacitor insulating film 3c-2 are formed, as shown in FIG. 56, tocomplete capacitors 3-2, in a manner similar to Embodiment 1.

According to Embodiment 2 as described above, the following effects canbe produced in addition to the effects produced by Embodiment 1.

(1) In forming the capacitors 3-2 each having the three fins 3a1-3a3,after the top surface of the conductive film 22f-2 for forming the firstfin 3a1-2 is flattened, the conductive films 22g-2, 22h-2 for formingthe second and third fins 3a2-1, 3a3-2 are formed on the flattened topsurface of the conductive film 22f-2, whereby good capacitors 3-2 can beformed more easily than the way the capacitors of Embodiment 1 arecreated, without extremely increasing the number of manufacturingprocesses.

(2) The insulating film 23d-2 for protection has previously been formedunder the conductive film 22f-2 for forming the first fin 3a1-2 so as tosandwich the predetermined insulating film 24f-2 therebetween, such thatthe insulating film 23d-2 is utilized as an etching stopper layer toremove the insulating film 24f-2. In this way, the lower surface of thefin 3a1-2 can also be used as a storage portion of the capacitor, sothat the total capacitance of the capacitor 3-2 can be made larger thanthe capacitor 3 of Embodiment 1.

(Embodiment 3)

FIGS. 57-65 are cross-sectional views each showing a main portion of asemiconductor substrate in a manufacturing process for a semiconductorintegrated circuit device according to a further embodiment of thepresent invention.

Briefly, Embodiment 3 differs from Embodiments 1, 2 in the method offorming capacitors which constitute memory cells. The method includes,for example, the following processes. It should be noted that ,forclarity of the drawings, the drawings used for illustrating Embodiment 3also omit the insulating film 9 formed on the side surface of the gateelectrode 2g, which is shown in FIG. 2.

FIG. 57 is a cross-sectional view showing a main portion of a memorycell array M-3 in a manufacturing process for the semiconductorintegrated circuit device according to Embodiment 3, which illustrates astructure similar to that created in the manufacturing process shown inFIG. 15 of Embodiment 1. A basic structure of nMOS 2-3 has already beenformed in an element forming region of a semiconductor substrate 1-3. Aninsulating film 24i-3 made of, for example, SiO₂ corresponds to theinsulating film 11a in FIG. 15. As shown in FIG. 57, after an insulatingfilm 24j-3 made of, for example, SiO₂ is deposited by the CVD method orthe like, contact holes 12a-3 each for exposing a portion of an n⁻ -typesemiconductor region 2a1-3 of the nMOS 2-3 are formed through theinsulating films 24i-3, 24j-3 by photolithography techniques, as shownin FIG. 58.

Subsequent to the formation of the contact holes 12a-3, a conductivefilm 22f-3 made of, for example, n-type low-resistance polysilicon isdeposited over the semiconductor substrate 1-3 by the CVD method or thelike, as shown in FIG. 59. Also in Embodiment 3, the conductive film22f-3 is deposited in this process to such a degree that the top surfacethereof becomes substantially planar. This conductive film 22f isprovided for forming a first fin for capacitors.

Thereafter, the top surface of the conductive film 22f-3 is etched backto further flatten the top surface of the conductive film 22f-3, asshown in FIG. 60.

Next, as shown in FIG. 61, after an insulating film 24g-3 made of, forexample, SiO₂ is deposited on the conductive film 22f-3 by the CVDmethod or the like, a conductive film 22g-3 made of, for example, n-typelow-resistance polysilicon is deposed on the top surface of theinsulating film 24g-3 by the CVD method or the like, followed by furtherdepositing an insulating film 24h-3 made of, for example, SiO₂ by theCVD method or the like. The conductive film 22g-3 is provided forforming the second fin for the capacitors.

Next, as shown in FIG. 62, contact holes 12f-3, each for exposing aportion of the conductive film 22f-3, are formed through the conductivefilm 22g-3 and the insulating films 24g-3, 24h-3 by photolithographytechniques. Then, as shown in FIG. 63, a conductive film 22h-3 made of,for example n-type low-resistance polysilicon is deposited over thesemiconductor integrated circuit 1-3 by the CVD method or the like. Thisconductive film 22h-3 is provided for forming the third fin for thecapacitors.

Briefly, in Embodiment 3, the top surface of the conductive film 22f-3for forming the first fin for the respective capacitors is flattened,and the conductor films 22g-3, 22h-3 for forming the second and thirdfins for the respective capacitors are deposited on the flattened topsurface. In this way, Embodiment 3 can more easily produce similareffects to those of the aforementioned Embodiment 1 without excessivelyincreasing the number of manufacturing processes, like the Embodiment 2.

Subsequent to the deposition of the conductive films 22g-3, 22h-3 forthe second and third fins, a resist pattern 20i-3 is formed on theconductive film 22h-3 for forming the capacitors by photolithographytechniques, and is used as an etching mask to pattern the conductivefilms 22g-3, 22h-3 and the insulating films 24g-3, 24h-3. In thisprocess, the conductive film 22f-3 for forming the first fin is used asa protection film which functions as a stopper for the etching.

In this way, the second and third fins 3a2-1, 3a3-3 for the capacitors3-3 are patterned as shown in FIG. 64. Subsequently, the insulating film24h-3 sandwiched between the second and third fins 3a2-3, 3a3-3 and theinsulating film 24g-3 sandwiched between the fin 3a2-3 and theconductive film 22f-3 are removed. Then, exposed portions of theconductive film 22f-3 are etched away to complete the capacitorelectrodes 3a for the respective capacitors 3-3, as shown in FIG. 65.

According to Embodiment 3 as described above, since the insulating film23d-2 for protection is not formed, the structure of Embodiment 3 has aneffect of simplifying the formation processes therefor, in addition tothe aforementioned effect (1) produced by Embodiment 2.

(Embodiment 4)

FIGS. 66-71 are cross-sectional views each showing a main portion of asemiconductor substrate in a manufacturing process for a semiconductorintegrated circuit device according to a further embodiment of thepresent invention.

In summary, Embodiment 4 differs from the aforementioned Embodiment 1 inthe method of forming the bit line conductors. The method is carriedout, for example, by the following processes.

FIGS. 66 and 67 are cross-sectional views respectively showing a mainportion of a memory cell array M-4 and a peripheral circuit region A-4in a manufacturing process for the semiconductor integrated circuitdevice according to Embodiment 4. The drawings illustrate the structuressimilar to those created at the manufacturing process shown in FIGS. 35and 36, wherein the insulating film 11a in FIGS. 35 and 36 is depictedas a flattened insulating film 11a-4 in FIGS. 66 and 67.

In the memory cell array M-4, the insulating film 11d-3 already has acontact hole 12b-3 formed therethrough so as to expose an n⁻ -typesemiconductor region 2a1-4 of an nMOS 2-4.

First, a conductive film 22i-4 made of, for example, n-typelow-resistance polysilicon is deposited over the semiconductor substrate1-4 as illustrated by the CVD method or the like.

The semiconductor substrate 1-4 is annealed, for example, in a N₂ gasatmosphere, so that the n-type impurity in the conductive film 22i-4 isdiffused into the substrate 1-4 to form an n⁺ -type semiconductor region2a2-4.

Subsequently, as shown in FIGS. 68 and 69, a resist pattern 20j-4 isformed by photolithography techniques so as to expose an upper portionof respective one semiconductor region 13a1-4, 14a1-4 of nMOS 13-4 andpMOS 14-4 in the peripheral circuit region A-4.

Then, contact holes 12c-4, each for exposing a portion of thesemiconductor regions 13a1-4, 14a1-4 of the nMOS 13-4 and PMOS 14-4 inthe peripheral circuit region 4-A, are formed through the insulatingfilm 11d-4, with the resist pattern 20j-4 used as an etching mask.

Next, as shown in FIGS. 70 and 71, after depositing a metal film 25a-4made of, for example, tungsten in a manner similar to the aforementionedEmbodiment 1, the metal film 25a-4 is patterned also in a manner similarto Embodiment 1 to form bit line conductors BL for memory circuits andfirst level wiring conductors 15a-4 (see FIG. 2) for peripheralcircuits, as has been described in connection with Embodiment 1.

It will therefore be understood that Embodiment 4 can also produceeffects similar to those listed in (3)-(5) of Embodiment 1.

While the invention made by the present inventors has been specificallydescribed on the basis of preferred embodiments thereof, it goes withoutsaying that the present invention is not limited to the above describedEmbodiments 1-4 but may be modified in various ways without departingfrom the gist thereof.

For example, while Embodiments 1-4 have been described for the casewhere the capacitors constituting memory cells each has a fin structure,the present invention is not limited to this particular structure butmay be variously modified. For example, as shown in FIG. 72, capacitors3-5 that have a crown structure may be employed.

The capacitors 3-5 are each constituted of a capacitor electrode 3a-5formed, for example, in a cylindrical shape, a capacitor insulating film3c-5 covering same, and a capacitor electrode 3b-5 further covering theinsulating film 3c-5. The capacitor electrode 3a-5 is electricallyconnected with an n⁻ -type semiconductor region 2a1-5 of an nMOS 2-5.The capacitor electrode 3b-5 is electrically connected with a poweringconductor 18-5 (see FIG. 4) and set at a predetermined potential. Thecapacitor electrodes 3a-5, 2b-5 are both made of, for example, n-typelow-resistance polysilicon, while the capacitor insulating film 3c-5 ismade of a lamination film consisting of, for example, a Si₃ N₄ layer anda SiO₂ layer. Alternatively, n-type low-resistance polysilicon may beutilized only for the capacitor electrode 3a-5; tungsten or TiN for thecapacitor electrode 3b-5; and tantalum oxide (Ta₂ O₅) for the capacitorinsulating film 3c-5, by way of example.

Also, while the Embodiments 1-3 have been described for the case wherethe bit line connection member BC is filled with low-resistancepolysilicon, the present invention is not limited to this particularstructure. Alternatively, as shown in FIG. 73, a pad film 26 made of,for example, n-type low-resistance polysilicon may be formed on thebottom of the bit line connection member BC. In this case, the bit lineconductors BL-5 may be made of, for example, tungsten or Al--Si--Cualloy. The capacitor electrode 3a-5 may have, for example, four fins3a1-5-3a4-5.

In this case, by forming the pad film 26 in a self-alignment manner, thespacing between nMOS's 2 on both sides of the bit line connection memberBC can be narrowed. In addition, since the top surface of the pad film26, if made somewhat wider, can attend to shifted contact holes 12b orthe like, the reliability with respect to the bit line conductors BL-5can be ensured even if the spacing between the nMOS's 2 is narrowed.Furthermore, since impurities can be diffused from the pad film 26toward the semiconductor substrate 1, the contact resistance of the nMOS2 to the semiconductor region 2a can be reduced. On top of that, themetal film for the bit line conductors may be used also as wiringconductors for constituting peripheral circuits.

Although Embodiment 4 has been described for the case where, for formingthe bit line conductors and the first level wiring conductors, contactholes reaching a semiconductor region of the MOS in the peripheralcircuit region are formed after the underlying low-resistancepolysilicon film 22i-4 (see FIG. 70) for constituting bit lineconductors is deposited on the insulating film 11d-4, the presentinvention is not limited to this procedure. Alternatively, the followingprocesses may be employed.

First, the underlying low-resistance polysilicon film 22i-4 for formingbit line conductors is deposited on the insulating film 11d-4, and thepolyilicon film 22i-4 is patterned such that it does not remain in theperipheral circuit region. Subsequently, contact holes reaching asemiconductor region of the MOS in the peripheral circuit region areformed through the insulating film 11d-4. After the formation of thecontact holes, a predetermined metal film is deposited over thesemiconductor substrate. Thereafter, the bit line conductors and thefirst level wiring conductors are formed by patterning the metal film.

While the present invention has been described for the case where thepresent invention is applied to a 64-megabit DRAM, which is a field ofindustrial utilization particularly related thereto, the presentinvention is not limited to this field, but may be applied to a varietyof fields. It is also possible to apply the present invention to DRAM'shaving different capacities such as 4-megabit or 16-megabit DRAM's, andto other semiconductor integrated circuit devices, for example, acomposite gate array having semiconductor memory circuits and so on.

We claim:
 1. A semiconductor memory device which has a memory cell arraysection and a peripheral circuit section, the memory cell array sectionincluding a plurality of memory cells, the memory cells includingswitching transistors, having a gate, a source and a drain, and aninformation storage element for each switching transistor, theperipheral circuit section including a MISFET having a gate, a sourceand a drain, the semiconductor memory device comprising:word lineconductors formed over the main surface of said semiconductor substratein said memory cell array section, said word line conductors functioningas gate electrodes of said switching transistors; a gate conductorformed over a main surface of a semiconductor substrate in saidperipheral circuit section, said gate conductor functioning as a gateelectrode of said MISFET; first semiconductor regions formed in saidsemiconductor substrate on both sides of each of said word lineconductors, said first semiconductor regions functioning as the sourceand drain of said switching transistor; second semiconductor regionsformed in said peripheral circuit section, said second semiconductorregions functioning as the source and drain of said MISFET; aninsulating film formed over said word line conductors and said gateconductor and having through-holes between said word line conductors soas to expose one of said first semiconductor regions of each switchingtransistor; a bit line connection member made of a polysilicon film andformed in each of said through-holes without extending over saidinsulating film; bit line conductors formed over said insulating filmand made of a tungsten film; and a wiring formed over said insulatingfilm in said peripheral circuit section and electrically connected toone of said source and drain of said MISFET, said wiring being made ofsaid tungsten film.
 2. A semiconductor memory device according to claim1, wherein said first semiconductor regions have a conductivity typeopposite to that of said second semiconductor regions.
 3. Asemiconductor memory device according to claim 2, wherein said firstsemiconductor regions have N-type conductivity and said secondsemiconductor regions have P-type conductivity.
 4. A semiconductormemory device according to claim 1, further comprising:first conductorsformed over said word lines and functioning as first electrodes of theinformation storage element; a dielectric film formed over each firstconductor; and a second conductor formed over each dielectric film andfunctioning as a second electrode of said information storage element.5. A semiconductor memory device according to claim 4, wherein saidfirst electrodes are electrically connected to the other of the sourceand drain regions of the switching transistors.
 6. A semiconductormemory device according to claim 5, wherein said first conductors aremade of a polysilicon film.